Defibrillators are implanted in patients susceptible to cardiac tachyarrhythmias including tachycardia or fibrillation. Such devices provide cardioversion or defibrillation by delivering a high voltage shock to the patient's heart, typically about 500-750 V. Current devices typically apply this voltage between two transvenously placed electrodes: one at the distal end of a lead inserted into the patient's right ventricle (RV), and the other in the superior vena cava (SVC) region. The lead normally extends from a pectorally or abdominally implanted defibrillator unit, through an incision in the patient's subclavian vein, and to the heart via the vein.
It is important to avoid movement of the lead after it is implanted in the proper position. Shifting of the electrode may also dangerously impair the efficacy of defibrillation shocks from the device by changing the locations across which the voltage is applied. In existing systems, a suture sleeve or collar may be included on the lead. The sleeve may be slid to a selected position on the lead, fixed to the lead in that position, and sutured to the vein or other adjacent tissue. Existing suture sleeves suffer a trade off between the desired attributes of low-resistance positioning and a snug and secure fit when properly positioned. A too tight sleeve will resist sliding along the lead during implantation, risking dislodging of the lead electrodes caused by unwanted motion of the lead. A too loose sleeve may allow the slippage that it was intended to prevent.
The preferred embodiment of the invention overcomes these limitations of the prior art by providing a suture sleeve having an elongated body defining a bore and having a relief aperture at a first intermediate position on the body and communicating with the bore. The sleeve includes a pair of actuator tabs connected to a second intermediate position on the body and extending therefrom, and at least a portion of the relief aperture is positioned between the tabs such that actuation of the tabs causes enlargement of the aperture.